"Richard W.M. Jones" <rjones@xxxxxxxxxx> writes: > The background to this is I've spent far too long trying to optimize > the conversion of qcow2 files to raw files. Most existing qcow2 files > that you can find online are zlib compressed, including the qcow2 > images provided by Fedora. Each cluster in the file is separately > compressed as a zlib stream, and qemu uses zlib library functions to > decompress them. When downloading and decompressing these files, I > measured 40%+ of the total CPU time is doing zlib decompression. This number may go even higher on s390x [1] because zlib-ng supports hardware acceleration. qatzip [2] and libnxz [3] should provide performance on the same order of magnitude for Intel and Power9 processors, with the negative side of not using a single library. > We already package zlib-ng in Fedora: > > https://src.fedoraproject.org/rpms/zlib-ng/blob/rawhide/f/zlib-ng.spec > https://github.com/zlib-ng/zlib-ng > > In my test zlib-ng is about 40% faster. > > Sadly zlib-ng is not compiled with the ZLIB_COMPAT option. What this > means in practice is that the zlib functions have different names > (eg. zng_inflateInit instead of inflateInit). It is not a drop-in > replacement for zlib and software would need to be adjusted to use it. > > However there is this bug / RFE to package the compat library. > > https://bugzilla.redhat.com/show_bug.cgi?id=2145239 > > It literally replaces /usr/lib64/libz.so.1, so pretty high stakes. It > has the appropriate Provides/Conflicts. > > Anyway, 40% (or whatever, but significant) performance improvement > sounds good for a very widely used operation. > > So I'd like to ask Fedora ... > > What do we think about the opt in approach of adding a patch similar > to the one proposed in bug 2145239, where I think you could "simply" > install zlib-ng to get better performance with existing software? > ("simply" because it seems high risk of going wrong) Wearing my zlib-ng fedora maintainer hat: I like the idea of this patch, although I think it needs a few changes. I'd like to merge it and add another package with the same source code, but different value for compat, i.e. package zlib-ng would still distribute the zlib-ng API while the new package would distribute the zlib-compatible API. That way, if there are any projects using the zlib-ng API, they could still be supported. [1] https://github.com/rust-lang/libz-sys/pull/72#issuecomment-904020105 [2] https://src.fedoraproject.org/rpms/qatzip [3] https://src.fedoraproject.org/rpms/libnxz -- Tulio Magno _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
